Ultraviolet-based gas sensor

ABSTRACT

A solution for evaluating a sample gas for a presence of a trace gas, such as ozone, is provided. The solution uses an ultraviolet source and an ultraviolet detector mounted in a chamber. The chamber can include reflecting walls and/or structures configured to guide ultraviolet light. A computer system can operate the ultraviolet source in a high power pulse mode and acquire data corresponding to an intensity of the ultraviolet radiation detected by the ultraviolet detector while a sample gas is present in the chamber. Using the data, the computer system can determine a presence and/or an amount of the trace gas in the sample gas.

REFERENCE TO RELATED APPLICATIONS

The current application is a continuation-in-part of U.S. patentapplication Ser. No. 13/863,437, filed on 16 Apr. 2013, which claims thebenefit of U.S. Provisional Application No. 61/624,716, filed on 16 Apr.2012, each of which is hereby incorporated by reference.

TECHNICAL FIELD

The disclosure relates generally to gas detection, and moreparticularly, to ultraviolet light emitting diode (UV LED)-based gasdetection.

BACKGROUND ART

Excess levels of ozone can be dangerous to the health of humans. As aresult, there are strict regulations regarding human exposure to largedoses of ozone. To warn the public of a high concentration of ozone inthe atmosphere, ozone levels are monitored using ozone detectors.Current ozone detectors generally fall into three classes: detectorsthat operate based on ozone light absorption; detectors that operatebased on semiconductor devices designed to sense ozone in air passedover the semiconductor device; and detectors that utilizeelectrochemical effects.

The detectors that operate based on ozone light absorption takeadvantage of the Beer-Lambert absorption law of ultraviolet (UV) lightpassing through ambient gas in a chamber that contains ozone. Sinceozone strongly absorbs UV radiation, a concentration of ozone can beinferred from a measured amount of UV absorption. The Beer-Lambert lawcan be applied to calculate the ozone concentration based on the UVabsorption detected using an optical source-detector couple. Typically,these devices utilize mercury discharge lamps, which necessitaterelatively large detectors with lamps having a limited operationallifetime. Additionally, these devices typically require a chamber havinga size in the tens of centimeters in order to successfully detect smalllevels of ozone.

The detectors that operate based on semiconductor devices designed tosense ozone in air passed over the semiconductor device have a highsensitivity not only to ozone, but other gases and trace elementspresent in the atmosphere, such as, for example, traces of organiccompounds. Calibration of these detectors may be less effective as thedevices age and/or interact with different environmental factorsaffecting an overall performance of the detector. The detectors thatutilize electrochemical effects often cannot accurately register smalllevels of ozone concentration present in the atmosphere, which,nevertheless, can be hazardous to human health.

SUMMARY OF THE INVENTION

Aspects of the invention provide a solution for evaluating a sample gasfor a presence of a trace gas, such as ozone. The solution uses anultraviolet source and an ultraviolet detector mounted in a chamber. Thechamber can include reflecting walls and/or structures configured toguide ultraviolet light. A computer system can operate the ultravioletsource in a high power pulse mode and acquire data corresponding to anintensity of the ultraviolet radiation detected by the ultravioletdetector while a sample gas is present in the chamber. Using the data,the computer system can determine a presence and/or an amount of thetrace gas in the sample gas.

A first aspect of the invention provides a system comprising: a chamber;an ultraviolet source mounted on a first interior side of the chamber;an ultraviolet detector mounted on the first interior side of thechamber, wherein the chamber is defined by a plurality of reflectingwalls having an ultraviolet reflection coefficient of at least eightypercent; and a computer system for evaluating a sample gas in thechamber for a presence of a trace gas by performing a method including:operating the ultraviolet source in a high power pulse mode; acquiringdata corresponding to an intensity of ultraviolet radiation detected bythe ultraviolet detector during the operating; and determining thepresence of the trace gas using the acquired data.

A second aspect of the invention provides a system comprising: a chamberhaving an inlet and an outlet; a pumping system for introducing a gasinto the chamber through the inlet; an ultraviolet source mounted on afirst interior side of the chamber; an ultraviolet detector mounted onthe first interior side of the chamber; and a computer system forevaluating a sample gas in the chamber for a presence of ozone byperforming a method including: operating the pumping system to introducethe sample gas into the chamber, wherein the operating includesoperating the pumping system with both the inlet and the outlet open fora sufficient time to allow at least three chamber volumes of gas toleave the chamber through the outlet; sealing the chamber; operating theultraviolet source in a high power pulse mode after the sealing;acquiring data corresponding to an intensity of ultraviolet radiationdetected by the ultraviolet detector during the operating; anddetermining the presence of ozone in the sample gas using the acquireddata.

A third aspect of the invention provides a method of evaluating a samplegas in a chamber for a presence of ozone, the method comprising: acomputer system operating a pumping system with a filter removing ozonefrom gas entering the chamber; the computer system operating the pumpingsystem without the filter removing ozone to introduce the sample gasinto the chamber, wherein the operating includes operating the pumpingsystem with both an inlet and an outlet of the chamber open for asufficient time to allow at least three chamber volumes of gas to leavethe chamber through the outlet; the computer system sealing the chamber;the computer system operating the ultraviolet source in a high powerpulse mode after the sealing; the computer system acquiring datacorresponding to an intensity of ultraviolet radiation detected by theultraviolet detector during the operating; and the computer systemdetermining the presence of ozone in the sample gas using the acquireddata.

Other aspects of the invention provide methods, systems, programproducts, and methods of using and generating each, which include and/orimplement some or all of the actions described herein. The illustrativeaspects of the invention are designed to solve one or more of theproblems herein described and/or one or more other problems notdiscussed.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the disclosure will be more readilyunderstood from the following detailed description of the variousaspects of the invention taken in conjunction with the accompanyingdrawings that depict various aspects of the invention.

FIG. 1 shows an illustrative environment for detecting a trace gas in anatmosphere according to an embodiment.

FIGS. 2A-2C show illustrative ozone detection components according toembodiments.

FIG. 3 shows another illustrative configuration of a chamber accordingto an embodiment.

FIG. 4 shows a chart of effective optical paths derived from simulatedray tracing results for various illustrative chamber shapeconfigurations according to an embodiment.

FIG. 5 shows an illustrative ozone detection component according to anembodiment.

FIG. 6 shows an illustrative beam guiding structure according to anembodiment.

FIG. 7 shows another illustrative beam guiding structure according to anembodiment.

FIG. 8 shows an illustrative process for calibrating an ozone detectioncomponent according to an embodiment.

FIG. 9 shows an illustrative process for measuring an ozoneconcentration in a sample gas according to an embodiment.

FIG. 10A shows absorption cross sections for various trace gases, whileFIGS. 10B-10C show illustrative schematics of trace gas detectioncomponents according to embodiments.

FIG. 11A shows an illustrative chemical detection component according toan embodiment, while FIG. 11B shows illustrative absorption within thechamber.

It is noted that the drawings may not be to scale. The drawings areintended to depict only typical aspects of the invention, and thereforeshould not be considered as limiting the scope of the invention. In thedrawings, like numbering represents like elements between the drawings.

DETAILED DESCRIPTION OF THE INVENTION

As indicated above, aspects of the invention provide a solution forevaluating a sample gas for a presence of a trace gas, such as ozone.The solution uses an ultraviolet source and an ultraviolet detectormounted in a chamber. The chamber can include reflecting walls and/orstructures configured to guide ultraviolet light. A computer system canoperate the ultraviolet source in a high power pulse mode and acquiredata corresponding to an intensity of the ultraviolet radiation detectedby the ultraviolet detector while a sample gas is present in thechamber. Using the data, the computer system can determine a presenceand/or an amount of the trace gas in the sample gas. The solution canprovide a compact detector, which can overcome one or more shortcomingsassociated with previous mercury lamp-based solutions. As used herein,unless otherwise noted, the term “set” means one or more (i.e., at leastone) and the phrase “any solution” means any now known or laterdeveloped solution.

Turning to the drawings, FIG. 1 shows an illustrative environment 10 fordetecting a trace gas, such as ozone, in an atmosphere according to anembodiment. To this extent, the environment 10 includes a computersystem 20 that can perform a process described herein in order to detecta presence and/or amount of a targeted trace gas in the atmosphere. Inparticular, the computer system 20 is shown including a detectionprogram 30, which makes the computer system 20 operable to detect and/ormeasure an amount of the targeted trace gas by performing a processdescribed herein.

The computer system 20 is shown including a processing component 22(e.g., one or more processors), a storage component 24 (e.g., a storagehierarchy), an input/output (I/O) component 26 (e.g., one or more I/Ointerfaces and/or devices), and a communications pathway 28. In general,the processing component 22 executes program code, such as the detectionprogram 30, which is at least partially fixed in storage component 24.While executing program code, the processing component 22 can processdata, which can result in reading and/or writing transformed datafrom/to the storage component 24 and/or the I/O component 26 for furtherprocessing. The pathway 28 provides a communications link between eachof the components in the computer system 20. The I/O component 26 cancomprise one or more human I/O devices, which enable a human user 12 tointeract with the computer system 20 and/or one or more communicationsdevices to enable a system user 12 to communicate with the computersystem 20 using any type of communications link. To this extent, thedetection program 30 can manage a set of interfaces (e.g., graphicaluser interface(s), application program interface, and/or the like) thatenable human and/or system users 12 to interact with the detectionprogram 30. Furthermore, the detection program 30 can manage (e.g.,store, retrieve, create, manipulate, organize, present, etc.) the data,such as detection data 40, using any solution.

In any event, the computer system 20 can comprise one or more generalpurpose computing articles of manufacture (e.g., computing devices)capable of executing program code, such as the detection program 30,installed thereon. As used herein, it is understood that “program code”means any collection of instructions, in any language, code or notation,that cause a computing device having an information processingcapability to perform a particular action either directly or after anycombination of the following: (a) conversion to another language, codeor notation; (b) reproduction in a different material form; and/or (c)decompression. To this extent, the detection program 30 can be embodiedas any combination of system software and/or application software.

Furthermore, the detection program 30 can be implemented using a set ofmodules 32. In this case, a module 32 can enable the computer system 20to perform a set of tasks used by the detection program 30, and can beseparately developed and/or implemented apart from other portions of thedetection program 30. As used herein, the term “component” means anyconfiguration of hardware, with or without software, which implementsthe functionality described in conjunction therewith using any solution,while the term “module” means program code that enables a computersystem 20 to implement the actions described in conjunction therewithusing any solution. When fixed in a storage component 24 of a computersystem 20 that includes a processing component 22, a module is asubstantial portion of a component that implements the actions.Regardless, it is understood that two or more components, modules,and/or systems may share some/all of their respective hardware and/orsoftware. Furthermore, it is understood that some of the functionalitydiscussed herein may not be implemented or additional functionality maybe included as part of the computer system 20.

When the computer system 20 comprises multiple computing devices, eachcomputing device can have only a portion of the detection program 30fixed thereon (e.g., one or more modules 32). However, it is understoodthat the computer system 20 and the detection program 30 are onlyrepresentative of various possible equivalent computer systems that mayperform a process described herein. To this extent, in otherembodiments, the functionality provided by the computer system 20 andthe detection program 30 can be at least partially implemented by one ormore computing devices that include any combination of general and/orspecific purpose hardware with or without program code. In eachembodiment, the hardware and program code, if included, can be createdusing standard engineering and programming techniques, respectively.

Regardless, when the computer system 20 includes multiple computingdevices, the computing devices can communicate over any type ofcommunications link. Furthermore, while performing a process describedherein, the computer system 20 can communicate with one or more othercomputer systems using any type of communications link. In either case,the communications link can comprise any combination of various types ofoptical fiber, wired, and/or wireless links; comprise any combination ofone or more types of networks; and/or utilize any combination of varioustypes of transmission techniques and protocols.

As discussed herein, the detection program 30 enables the computersystem 20 to detect a presence of and/or measure an amount of a targetedtrace gas in an atmosphere. Additional aspects of the invention areshown and described in conjunction with the detection and/or measurementof an amount of ozone in an atmosphere, such as the earth's atmosphere,an atmosphere in a workplace environment, an atmosphere in an enclosedenvironment (e.g., a submarine), and/or the like. However, it isunderstood that various other trace gases can be targeted in anyatmosphere using the teachings described herein.

The computer system 20 can operate various devices included in the ozonedetection component 40 in order to detect and/or measure an amount ofozone in the atmosphere. During operation of the various devices in theozone detection component 40, the computer system 20 can receive andprocess detection data 34 to evaluate the atmosphere for the presence ofozone. The computer system 20 can store data corresponding to theevaluation (e.g., a result, a timestamp, and/or the like) as detectiondata 34. Furthermore, the computer system 20 can provide some or all ofthe detection data 34 for use by the user 12. The detection data 34 caninclude, for example, a level of the ozone detected, an alarm conditiongenerated in response to a level of ozone detected, and/or the like. Inresponse to receiving the detection data 34, the user 12 can take any ofvarious actions.

FIGS. 2A-2C show illustrative ozone detection components 40A-40Caccording to embodiments. As shown in FIG. 2A, an ozone detectioncomponent 40A can include a chamber 42, an ultraviolet source 44, and anultraviolet detector 46. The ultraviolet source 44 and the ultravioletdetector 46 can be located in a close proximity to each other. Asillustrated, the ultraviolet source 44 can be configured to emitultraviolet light 48 into the chamber 42, and the ultraviolet detector46 can be configured to detect the ultraviolet light 48 after it travelsthrough the chamber 42. When acquiring measurement data, the ultravioletsource 44 can be operated in a pulsed mode delivering maximumultraviolet power into the chamber 42. For example, the pulsed mode canhave a frequency up to approximately one gigahertz, and can assist infiltering noise in the data acquired by the ultraviolet source 44. Thechamber 42 can have any size. For example, the chamber 42 can havedimensions between approximately ten and approximately thirty cubiccentimeters.

In an embodiment, the ultraviolet source 44 is an ultraviolet lightemitting diode (LED). In a more particular embodiment, the ultravioletLED is a deep ultraviolet LED configured to emit ultraviolet light 48having a peak wavelength between approximately 240 and approximately 290nanometers. The ultraviolet source 44 can be a group III-nitride basedsemiconductor. Illustrative group III-nitride based LEDs include layersformed from alloys of any of various combinations of one or more of:boron (B); indium (In); aluminum (Al); and gallium (Ga), and nitrogen(N). Such a layer can be of the form Ga_(z)In_(y)Al_(x)B_(1-x-y-z)N,where x, y, and z indicate the molar fraction of a given element, where0≤x, y, z≤1, and where 0≤x+y+z≤1.

In an embodiment, the ultraviolet source 44 is configured to emitultraviolet light 48 having a prescribed angular distribution such thatultraviolet rays emitted at different angles travel, in general,different optical paths prior to being detected by the ultravioletdetector 46. For example, the ultraviolet source 44 can include a devicestructure formed (e.g., epitaxially grown) on a substrate through whichthe ultraviolet light will be emitted from the ultraviolet source 44.The substrate can comprise any suitable substrate including, forexample, sapphire, AlN, GaN, AlGaN, zinc oxide (ZnO), lithium gallate(LiGaO₂), lithium aluminate (LiAlO₂), and/or the like. The exteriorsides of the substrate can be shaped (e.g., tapered) to control theangular distribution of ultraviolet light 48 from the ultraviolet source44 using any solution (e.g., an etching process, scribed with a laser,and/or the like).

It is understood that while the ultraviolet source 44 is shown locatedwithin the chamber 42, other solutions can be implemented for emittingultraviolet light 48 within the chamber 42. For example, an ultravioletsource 44 can be located external to the chamber 42, and ultravioletlight 48 can be directed from the ultraviolet source 44 into the chamber42 using wave guiding means (e.g., optical fiber(s)). In this case,multiple optical fibers can extend into the chamber 42 and be configuredto emit ultraviolet light 48 having the prescribed angular distribution.Similarly, it is understood that two or more ultraviolet sources 44 canbe used to generate ultraviolet light 48 within the chamber 42.

The ultraviolet detector 46 can comprise any type of device whoseoperation is altered in response to one or more properties of incidentultraviolet light having a wavelength within a target range ofwavelengths. For example, one or more attributes of a signal generatedby the ultraviolet detector 46 can be altered based on a presence of theultraviolet radiation, an amount of the ultraviolet radiation, and/orthe like, which is incident to a detecting surface of the ultravioletdetector 46. Furthermore, the ultraviolet detector 46 can havesufficient sensitivity to enable measurement data having a desiredaccuracy. For example, the ultraviolet detector 46 can have asensitivity of approximately one microwatt per square centimeter. In anembodiment, the ultraviolet detector 46 is a photodetector. In anotherembodiment, the ultraviolet detector 46 comprises an ultraviolet LEDoperated in reverse bias. In a further embodiment, both the ultravioletsource 44 and the ultraviolet detector 46 are devices capable of beingoperated as an emitting device (e.g., when operated under forward bias)or a detecting device (e.g., when operated under reverse bias). In thiscase, the computer system 20 (FIG. 1) can change operation of thedevices using any solution (e.g., alternating source/detector, changingthe operation after a period of operation, and/or the like). While asingle ultraviolet detector 46 is shown, it is understood that the ozonedetection component 40A can include any number of one or moreultraviolet detectors 46.

The chamber 42 is shown formed by a chamber floor 50 and a plurality ofchamber walls 52A-52E. In an embodiment, the chamber floor 50 comprisesa material having a low thermal expansion. For example, the material cancomprise a metal, such as that used in the transistor outline (TO)package, TO-39, or a similar package. The chamber floor 50 can includesets of pins 54A, 54B for use in connecting each of the ultravioletdevices 44, 46, respectively, to a circuit (e.g., the computer system 20shown in FIG. 1). The chamber walls 52A-52E can be formed of anysuitable material. The material can be reflective of ultravioletradiation having the target wavelength and/or can be coated with amaterial reflective of ultraviolet radiation. In either case, thechamber walls 52A-52E can have an ultraviolet reflection coefficient ofat least eighty percent. For example, the chamber walls 52A-52E can beformed of or covered by highly ultraviolet-reflective aluminum.

Each of the chamber walls 52A-52E is shown having a substantially flatinterior surface. In an embodiment, the chamber 42 is defined by one ormore chamber walls having a parabolic interior surface. For example,FIG. 2B shows an illustrative ozone detection component 40B in which thechamber walls 56A, 56E have a parabolic shape, while the chamber walls56B-56D are substantially flat surfaces. Similarly, FIG. 2C shows anillustrative ozone detection component 40C in which the chamber walls58A, 58B, 58D, 58E have interior surfaces of parabolic shapes while thechamber wall 58C has a substantially flat interior surfaces. In eithercase, the parabolic shapes can be configured to increase a number ofreflections of the ultraviolet radiation prior to being detected by theultraviolet detector.

Returning to FIG. 2A, the ozone detection component 40A further includesan inlet 60 and an outlet 62. During operation of the ozone detectioncomponent 40A, a sample gas (e.g., air from the earth's atmosphere) canbe selectively introduced into the chamber through the inlet 60, and gascan be selectively allowed to leave the chamber through the outlet 62.To this extent, the inlet 60 and the outlet 62 can each include a valve,or the like, which is operable (e.g., by the computer system 20), toallow or not allow the flow of a gas through the corresponding opening.

A pumping system 64 can be located adjacent to the inlet 50, and can beoperated (e.g., by the computer system 20) to force a gas into thechamber 42. The pumping system 64 can comprise any type of pumpingsystem 64, such as a vacuum pump, a fan, and/or the like, which can beoperated to draw the gas into the chamber 42 at a target pressure. It isunderstood that while the pumping system 64 is shown located adjacent tothe inlet 50, a pumping system can be located adjacent to the outlet 62.In this case, such a pumping system can be operated to force gas out ofthe chamber 42, thereby causing a gas to enter the chamber through theinlet 60.

The ozone detection component 40A also is shown including a filteringunit 66 located adjacent to the inlet 60 (e.g., between the inlet 60 andthe pumping system 64). The filtering unit 66 can comprise a combinationof one or more of any type of filter capable of filtering large (e.g.,few microns size) and/or small (e.g., 0.3 microns) elements that may bepresent in the atmosphere. Additionally, the filtering unit 66 caninclude one or more filters capable of filtering ultraviolet absorbingmaterials and gases other than the target trace gas (e.g., ozone), suchas organic and other ultraviolet absorbing trace elements. These filtersin the filtering unit 66 can be fixed in place such that the gasentering the chamber 42 always has been filtered of the target elements,materials, and/or gases. The filtering unit 66 can include a cleaningmechanism, a monitor for indicating when a filter requirescleaning/changing, and/or the like, which can be operated by thecomputer system 20 using any solution.

Additionally, the filtering unit 66 can include one or more filters 67,which are capable of being operated by the computer system 20 toselectively filter the gas entering the chamber 42. In an embodiment,the filtering unit 66 includes a filter 67 corresponding to the targettrace gas (e.g., ozone), which can be selectively utilized to remove asubstantial portion of any of the target trace gas present in the gasprior to its entering the chamber. For example, the filtering unit 66can include a filter 67 including a catalyst, which converts ozone intooxygen and by-product elements. The filtering unit 66 can be configuredto enable selective use of the filter 67 using any solution. Forexample, the filtering unit 66 can be configured to move/remove thefilter 67 from an air flow path, redirect an air flow path (e.g., usingone or more deflectors, or the like) to pass through/not pass throughthe filter 67, and/or the like.

The ozone detection component 40A also is shown including a target tracegas source 68, which can be operated by the computer system 20. Inparticular, the target trace gas source 68 can produce the target tracegas (e.g., ozone) at any of a set of known concentrations and deliverthe target trace gas into the chamber 42 (e.g., via another inlet). Inan embodiment, the target trace gas source 68 comprises an ozonegenerating device, which can generate ozone using any solution (e.g., adischarge arc) and can be selectively operated by the computer system 20to generate gas having any of a plurality of known concentrations ofozone. A range of the known concentrations can be selected based on anaccuracy of the ozone detection component 40A and a range ofexpected/critical measurement values for the trace gas. In anembodiment, the trace gas is ozone and the range of known concentrationsvaries between approximately 0.1 ppm to approximately 2 ppm.

It is understood that the chamber 42 and the chamber walls 52A-52E areonly illustrative of various possible configurations of a chamber forthe ozone detection component 40A. To this extent, FIG. 3 shows anotherillustrative chamber configuration according to an embodiment. In thiscase, an interior of the chamber is formed by a chamber floor 50, afirst conical frustum (truncated cone) 70A attached thereto, and asecond conical frustum 70B attached to the first conical frustum 70A.Each conical frustum 70A, 70B has an interior surface that is reflectiveof ultraviolet radiation. The conical frustums 70A, 70B are configuredsuch that they are attached at their respective bases, which aresubstantially the same size. A top of the first conical frustum isattached to the chamber floor 50, and a top of the second conicalfrustum forms a top surface of the interior of the chamber.

Each conical frustum 70A, 70B is characterized by a correspondingopening angle Θ₁, Θ₂, respectively, and a corresponding height h₁, h₂,respectively. In an embodiment, a shape of the interior of the chamberis configured to result in a target effective optical path thatultraviolet light emitted by the ultraviolet source 44 travels beforeimpinging the ultraviolet detector 46. For example, the target opticalpath can be selected to be at least a minimum length. To this extent,the opening angles Θ₁, Θ₂ and/or heights h₁, h₂ can be configured toprovide an effective optical path having a minimum length.

FIG. 4 shows a chart of effective optical paths derived from simulatedray tracing results for various illustrative chamber shapeconfigurations according to an embodiment. A cross section of thechamber shape corresponding to each of the effective optical paths isshown below the corresponding bar. As illustrated, variation in theopening angles Θ₁, Θ₂ affects the length of the effective optical path.In the ray tracing simulations, the longest effective optical path wasachieved with opening angles Θ₁, Θ₂ of approximately thirty and fortydegrees, respectively. In an embodiment, each of the opening angles Θ₁,Θ₂ is within a range between approximately twenty degrees andapproximately fifty degrees. Using the selected angles Θ₁, Θ₂, thecorresponding heights h₁, h₂ can be selected to increase/decrease thevalue of the effective optical path. Illustrative dimensions used in thesimulation are four millimeters for the height h₁, 2.4 millimeters forthe height h₂, bottom radiuses of each conical frustum 70A, 70B of 4.5millimeters, and top radiuses of each conical frustum 70A, 70B of 2.5millimeters.

While the embodiments of FIGS. 2A-2C and FIG. 3 describe use of diffuselight, it is understood that collimated ultraviolet light can be used.Use of collimated ultraviolet light also can enable an effective opticalpath to be increased without requiring a significant increase in thevolume of the chamber 42. The collimated ultraviolet light can begenerated, for example, by an ultraviolet laser diode. Alternatively, adiffuse ultraviolet LED can generate diffuse ultraviolet light, which issubsequently collimated using, for example, a parabolic reflector.

To this extent, FIG. 5 shows an illustrative ozone detection component40D according to an embodiment. While not shown for clarity, it isunderstood that the ozone detection component 40D can include variouscomponents shown in FIG. 2A. In this case, an ultraviolet source 44 islocated at a focal point of a parabolic reflector 72. During operation,the ultraviolet source 44 emits diffuse ultraviolet light, whichreflects off of the parabolic reflector 72, producing a collimated beamof ultraviolet light 74. A size of the ultraviolet source 44 can berelatively small compared to a diameter of the parabolic reflector 72.In an embodiment, the diameter of the parabolic reflector 72 is at leastapproximately five times greater than a characteristic size of theultraviolet source 44. In a further embodiment, the ultraviolet source44 has sub-millimeter dimensions. The parabolic reflector 72 can beformed of/coated with any material highly reflective of ultravioletlight, such as highly ultraviolet-reflective aluminum.

The chamber 42 also is shown including various beam guiding components.The beam guiding components can be configured to direct the ultravioletbeam 74 onto a surface of the ultraviolet detector 46. Furthermore, thebeam guiding components can be configured to cause the ultraviolet beam74 to travel an effective optical path of a minimum target length. Forexample, the chamber 42 is shown including a forty-five degree prism 76,which is configured to redirect, e.g., through total internalreflection, the ultraviolet beam 74 onto a grooved plate structure 80.The grooved plate structure 80 includes two grooved plates 82A, 82B,which are positioned in a staggered arrangement. The staggeredarrangement of the grooved plates 82A, 82B is configured to cause theultraviolet beam 74 to reflect back and forth between the grooved plates82A, 82B before eventually being redirected onto the ultravioletdetector 46 by a prism 78. It is understood that the grooved platestructure 80 is only illustrative of various possible arrangements ofoptical elements, which can be utilized to increase an optical pathtraveled by the ultraviolet beam 74.

The grooved plate structure 80 can be fabricated using any solution. Inan embodiment, each prism 76, 78 and each of the grooved plates 82A, 82Bis fabricated of an ultraviolet transparent material having an index ofrefraction greater than approximately 1.42 for ultraviolet light havinga wavelength corresponding to the peak wavelength emitted by theultraviolet source 44. Illustrative ultraviolet transparent materialsinclude fused silica, alumina sol-gel glass, alumina aerogel, sapphire,aluminum nitride (e.g., single crystal aluminum nitride), boron nitride(e.g., single crystal boron nitride), and/or the like. The groovedplates 82A, 82B can be fabricated by machining the grooves in theultraviolet transparent material, with the angle 84 between groovesbeing ninety degrees. A dimension of each groove (e.g., a length of oneof the sides of the prism) can be selected to be substantially larger(e.g., at least two times) than a diameter of the ultraviolet beam 74.

Each grooved plate 82A, 82B also can have an antireflective coating 86A,86B formed thereon using any solution. For example, the antireflectivecoating 86A, 86B can comprise an ultraviolet transparent material with anano-scale roughness on the order of the wavelength of the ultravioletbeam 74. To this extent, a characteristic scale of the variationprovided by the nano-scale roughness can be between approximately ten totwo hundred percent of the wavelength of the ultraviolet beam 74.

The grooved plate structure 80 can be designed such that any Fresnelreflected ultraviolet light travels the same path as the ultravioletbeam 74, but in the opposite direction. Such Fresnel radiation entersthe parabolic reflector 72 and is reflected back towards the ultravioletdetector 46. Regardless, the Fresnel reflectance for normal incidentlight at an air/prism interface can be relatively small. For example, aprism with refractive index of 1.42 has a Fresnel reflectance of 2.7%.

In an embodiment, one or more of the optical components of the ozonedetection component 40D can be movable. For example, as indicated by thearrow 88A, the prism 76 can be moved over a range of distances furtherand closer to the parabolic reflector 72. Similarly, as indicated byarrows 88B, 88C, one or both of the grooved plates 82A, 82B of thegrooved plate structure 80 can be moved over a range of distances closerto and further from the ultraviolet detector 46. Movement of thecomponents can be implemented using any solution. For example, in anembodiment, the computer system 20 (FIG. 1) can operate a linearactuator, such as a rack and pinion, and/or the like, for the movement88A-88C. While certain components of the ozone detection component 40Dare shown as movable, it is understood that this is only illustrativeand other optical components and combinations of optical components canbe movable in other embodiments.

The motion can be used to adjust one or more aspects of the operation ofthe ozone detection component 40D. For example, the motion can be usedto adjust a focus of the ultraviolet beam 74. Additionally, the motioncan be used to adjust an intensity of ultraviolet radiation impingingthe ultraviolet detector 46, e.g., by altering a number of times theultraviolet beam 74 is reflected, thereby altering the length of theoptical path of the ultraviolet beam 74. For example, for accuratemeasurements of absorption, the computer system 20 can choose an opticalpath to be as long as possible while minimizing absorption by chamberelements, such as the reflective surfaces of the grooved plate structure80. In an embodiment, the computer system 20 can implement anoptimization procedure that includes movement of one or more of theoptical components to result in a largest ratio of UV intensity detectedwithout a presence of gas to the UV intensity detected with the presenceof gas.

While the grooved plate structure 80 is illustrated as providing twodimensional guiding of the ultraviolet beam 74, it is understood that anembodiment can provide three-dimensional wave guiding, thereby furtherincreasing an optical path of the ultraviolet beam 74. For example, FIG.6 shows an illustrative beam guiding structure 90 according to anembodiment. The beam guiding structure 90 includes a pair of groovedplates 92A, 92B, which can be fabricated and arranged in the same manneras the grooved plates 82A, 82B (FIG. 5) described herein. To thisextent, an ultraviolet source 44 can emit an ultraviolet beam, whichtravels a first path 74A through the beam guiding structure 90.

The beam guiding structure 90 includes a prism 98A on a first end of agrooved plate 92A, which redirects the ultraviolet beam from the firstpath 74A to a second path 74B through the beam guiding structure 90.Similarly, the beam guiding structure 90 includes a prism 98B on asecond end of a grooved plate 92B, which redirects the ultraviolet beamfrom the second path 74B to a third path 74C through the beam guidingstructure 90. While not shown for clarity, the beam guiding structure 90can include any number of prisms configured to cause the ultravioletbeam to travel any number of paths through the beam guiding structure90. An extent to which the optical path can be increased depends on adegree of light collimation, e.g., achieved by the parabolic reflector72 (FIG. 5), which in turn depends on a size of the ultraviolet source44 and its characteristic angular distribution of intensity. Regardless,eventually, a prism 98C can redirect the ultraviolet beam out of thebeam guiding structure 90 and into a path 74D which terminates at asurface of an ultraviolet detector 46.

FIG. 7 shows another illustrative beam guiding structure 91 according toan embodiment. In this case, the beam guiding structure 91 comprises aFabry-Perot cavity formed by a pair of Bragg reflecting mirrors 93A,93B. The Bragg reflecting mirrors 93A, 93B can include dielectric layers(e.g., silicon dioxide) with varying reflectivity of the ultravioletradiation. The widths of the layers in the Bragg reflecting mirrors 93A,93B can be selected based on the wavelength of radiation emitted by anultraviolet source 44. The beam guiding structure 91 can be used inconjunction with an ultraviolet source 44 capable of being moved (e.g.,rotated) by the computer system 20 (FIG. 1). The motion 95 can result ina different angular position of the ultraviolet beam emitted by theultraviolet source 44 with respect to the surface normal of the Braggreflecting mirrors 93A, 93B. The computer system 20 can adjust the angleto change a length of an optical path of the ultraviolet radiation priorto its being detected by the ultraviolet detector 46. As discussedherein, the computer system 20 can implement an optimization procedurein which the angular position of the ultraviolet source 44 is selectedto yield a largest ratio of ultraviolet intensity detected without thepresence of a gas to the ultraviolet intensity detected with thepresence of the gas. In an embodiment, the computer system 20 canacquire measurement data for several optical path lengths.

Returning to FIGS. 1 and 2A, the computer system 20 can be configured tooperate the various devices of the ozone detection component 40A in botha calibration mode and a measurement mode. In an embodiment, thecomputer system 20 can periodically (e.g., in response to a request froma user 12, based on an amount of operating time, and/or the like)operate the various devices of the ozone detection component 40A in thecalibration mode to re-calibrate the ozone detection component 40A. Suchre-calibration may be desired to, for example, account for subtlechanges in the chamber 42 environment which may be present due tovarious deposits building up on the chamber walls 52A-52E therebyaffecting the measurements acquired using the ultraviolet detector 46.

The computer system 20 can calibrate the ozone detection component 40Ato empirically determine ultraviolet absorption calibration data forvarious ozone concentrations, which the computer system 20 can store asdetection data 34. To this extent, FIG. 8 shows an illustrative processfor calibrating the ozone detection component 40A, which can beimplemented by the computer system 20, according to an embodiment.

In action A102, the computer system 20 can remove ozone from the chamber42 using any solution. For example, the computer system 20 can operatethe filtering unit 66 to activate an ozone filter 67 included therein toremove a substantial portion of any ozone present in the gas prior toits entering the chamber 42. While the ozone filter 67 is activated, thecomputer system 20 can operate the pumping system 64 to causeozone-filtered gas to enter the chamber 42 through the inlet 60. For aninitial startup period, the computer system 20 can open the outlet 62 toallow gas to evacuate the chamber 42 there through. In an embodiment,the initial startup period lasts for an amount of time to allow at leastseveral chamber volumes of gas to evacuate the chamber 42.

In action A104, the computer system 20 can acquire data corresponding toan intensity of the ultraviolet radiation detected by the ultravioletdetector 46. For example, the computer system can turn off the pumpingsystem 64 and seal the chamber 42, e.g., by closing both the outlet 62and the inlet 60. Additionally, the computer system 20 can operate theultraviolet source 44 to emit ultraviolet radiation 48, and obtain datacorresponding to a detected intensity of the ultraviolet radiation 48from the ultraviolet detector 46. The computer system 20 can store thedata as detection data 34 corresponding to a reference ultravioletintensity at a zero ozone level.

In action A106, the computer system 20 can determine whether data is tobe required for another known ozone concentration as part of thecalibration process. If so, in action A108, the computer system 20 canintroduce gas having a known concentration of ozone into the chamber 42using any solution. For example, the computer system 20 can operate thetarget trace gas source 68, which can be configured to generate a gaswith one of a plurality of possible ozone levels and introduce the gasinto the chamber 42. For an initial startup period, the computer system20 can open the outlet 62 to allow gas to evacuate the chamber 42 therethrough. In an embodiment, the initial startup period lasts for anamount of time to allow at least several chamber volumes of gas toevacuate the chamber 42.

In action A110, the computer system 20 can acquire data corresponding toan intensity of the ultraviolet radiation detected by the ultravioletdetector 46. For example, the computer system can turn off the targettrace gas source 68 and seal the chamber 42, e.g., by closing the outlet62. Additionally, the computer system 20 can operate the ultravioletsource 44 to emit ultraviolet radiation 48, and obtain datacorresponding to a detected intensity of the ultraviolet radiation 48from the ultraviolet detector 46. The computer system 20 can store thedata as detection data 34 corresponding to an ultraviolet intensity atthe corresponding ozone level.

After acquiring the data for an ozone level, the computer system 20 candetermine whether data is to be required for another known ozoneconcentration as part of the calibration process. If so, the computersystem 20 can repeat actions A108 and A110 for the next ozoneconcentration. In an embodiment, the computer system 20 acquires datafor a plurality of non-zero known ozone concentrations as part of thecalibration process. Additionally, the computer system 20 can acquirethe data by gradually increasing the known ozone concentration in eachrepetition of actions A108 and A110. Any number of known ozoneconcentrations can be used over any span of ozone concentrations. In anembodiment, at least the highest known ozone concentration used in thecalibration process is higher than an ozone concentration at which analarm is indicated. For example, the calibration process can use ozoneconcentrations ranging from 0.1 ppm to 2 ppm, with increments of 0.1ppm.

In any event, once all of the ozone concentration data has beenacquired, in action A112, the computer system 20 can process theacquired concentration data to generate calibration data for the ozonedetection component 40A. For example, the computer system 20 can createa reference table, which is stored as detection data 34, including themeasured ultraviolet intensity for each of the known ozoneconcentrations. Furthermore, the computer system 20 can determine anamount of ultraviolet light absorbed at each of the known ozoneconcentrations, which can be stored in the reference table.Additionally, the computer system 20 can use the acquired measurementdata to generate a calibration curve (e.g., using a curve-fittingsolution), which the computer system 20 can store as detection data 34.

The computer system 20 can subsequently use the calibration data tomeasure an ozone concentration in sample gas(es). To this extent, FIG. 9shows an illustrative process for measuring an ozone concentration in asample gas, which can be implemented by the computer system 20 using theozone detection component 40A, according to an embodiment.

Initially, the computer system 20 can determine whether the calibrationdata remains valid. To this extent, in action A202, the computer system20 can remove ozone from (or provide a known ozone concentration to) thechamber 42 and in action A204, the computer system 20 can acquire datacorresponding to an intensity of the ultraviolet radiation detected bythe ultraviolet detector 46 using any solution. For example, thecomputer system 20 can implement a solution similar to that described inconjunction with calibrating the ozone detection component 40A. Inaction A206, the computer system 20 can determine whether the intensityof the ultraviolet radiation agrees with the zero ozone level (or theknown ozone concentration) reference ultraviolet intensity. If not, inaction A208, the computer system 20 can re-calibrate the ozone detectioncomponent 40A using any solution. Furthermore, the computer system 20can provide a warning for presentation to a user 12. In an embodiment,the computer system 20 can use one or more additional or alternativeozone concentrations as part of validating the calibration data.

When the computer system 20 successfully validates the calibration data,in action A210, the computer system 20 can remove ozone from the chamber42 using any solution, e.g., by operating the filtering unit 66 toactivate an ozone filter 67, operating the pumping system 64 to causeozone-filtered sample gas to enter the chamber 42, and/or the like, asdescribed herein. In action A212, the computer system 20 can introducethe sample gas into the chamber 42 using any solution. In an embodiment,the computer system 20 creates a partial vacuum in the chamber 42 priorto introducing the sample gas. For example, the computer system 20 canoperate the pumping system 64 to cause air in the chamber 42 to bepumped out through the inlet 60 while the outlet 62 is closed.

Subsequently, the sample gas is flown into the chamber 42 (e.g., via theinlet 60 and/or the outlet 62) until the gas pressure inside the chamber42 is approximately equal to the gas pressure outside the chamber 42.The computer system 20 can further operate the pumping system 64 to flowsample gas into the chamber 42 while the outlet 62 is open to allow gasto escape from the chamber 42. In an embodiment, the computer system 20can operate the pumping system 64 for a sufficient amount of time toallow at least several (e.g., three) chamber volumes of gas to flowthrough the outlet 62.

In action A214, the computer system 20 can acquire data corresponding toan intensity of the ultraviolet radiation detected by the ultravioletdetector 46 using any solution. For example, the computer system 20 canseal the chamber 42 (e.g., by stopping the pumping system 64, closingthe inlet 60, closing the outlet 62, and/or the like). The computersystem 20 also can operate the ultraviolet source 44 to emit ultravioletradiation 48, and obtain data corresponding to a detected intensity ofthe ultraviolet radiation 48 from the ultraviolet detector 46. Thecomputer system 20 can store the data as detection data 34.

In action A216, the computer system 20 can determine an ozoneconcentration in the sample gas using the data corresponding to thedetected intensity of the ultraviolet radiation 48 and the calibrationdata. For example, the computer system 20 can: compare the detectedintensity to the reference table to deduce the ozone concentration;interpolate the data based on the reference table to find the ozoneconcentration; use the calibration curve to determine the ozoneconcentration; and/or the like.

It is understood that the process described herein for evaluating anozone concentration in a sample gas is only illustrative of varioussolutions. For example, in an embodiment, the computer system 20 candetermine the ozone concentration based on ultraviolet absorption usingthe Beer-Lambert absorption law. In this case, sufficiently accurateknowledge of a length of the optical path of the ultraviolet radiationis required, which can be available, for example, when collimatedultraviolet radiation is used as described herein.

In an embodiment, the ozone detection component 40A can include one ormore additional devices, which can be utilized to obtain more accuratemeasurement data for the ozone concentration. To this extent, the ozonedetection component 40A is shown including a temperature sensor 61 and apressure sensor 63, each of which can provide data corresponding to thesample gas (e.g., the atmosphere surrounding the ozone detectioncomponent 40A) to the computer system 20. The computer system 20 canaccount for the temperature and/or pressure when generating and/or usingthe calibration data. For example, the computer system 20 can generateand utilize multiple sets of calibration data, each of which correspondsto a unique temperature/pressure combination. Furthermore, when thetemperature/pressure of a sample gas differs from that of any of thesets of calibration data, the computer system 20 can generate anotherset of calibration data and/or utilize an ozone concentration derived bycombining ozone concentration values obtained from multiple sets ofcalibration data (e.g., calibration data corresponding to the closestlower and closest higher temperatures).

While shown and described in conjunction with detecting ozone, it isunderstood that this is only illustrative, and embodiments can beutilized to detect a presence and/or determine a concentration of any ofvarious types of trace gases. Other illustrative trace gases includenitric oxide (NO), chlorine dioxide (ClO₂), sulfur dioxide (SO₂), and/orthe like. An embodiment of a detection component described herein can beconfigured to distinguish between and/or detect a presence of any ofvarious types of gases. To this extent, in an embodiment, a detectioncomponent can comprise multiple ultraviolet sources configured to emitultraviolet light having distinct peak wavelengths. The computer system20 can selectively operate the ultraviolet sources to emit ultravioletradiation of one or more peak wavelengths. The peak wavelengths can beselected based on the trace gas to be evaluated. For example, asillustrated in FIG. 10A, different trace gases have different absorptioncross sections and a peak wavelength can correspond to an absorptionpeak of a trace gas. The computer system 20 can select one or more peakwavelengths to differentiate between different trace gases, identify aparticular trace gas, and/or the like. Illustrative peak wavelengthranges include: 270-290 nm; 210-250 nm; and 300-360 nm. Embodiments caninclude one or more ultraviolet sources that emit ultraviolet radiationin any combination of one or more of these ranges and/or other peakwavelength ranges.

FIG. 10B shows an illustrative schematic of a trace gas detectioncomponent 100 according to an embodiment. As illustrated, the trace gasdetection component 100 can include multiple ultraviolet sources, suchas the ultraviolet sources 44A, 44B, that operate different peakwavelengths. For example, the ultraviolet sources can include one ormore ultraviolet sources that operate at a peak wavelength ofapproximately 275 nanometers with a full width at half maximum (FWHM) ofabout 20 nanometers, and one or more other ultraviolet sources thatoperate at a peak wavelength of approximately 230 nanometers. However,it is understood that these peak wavelengths are only illustrative. Ingeneral, the ultraviolet peaks can be separated by at least half of theFWHM or more. To this extent, the separation should be at least a fewnanometers, and on the order of ten nanometers in an embodiment.

In FIG. 10B, the ultraviolet sources 44A, 44B can direct ultravioletlight of different wavelengths towards a mirror 102, which reflects theultraviolet light onto a surface of a detector 46. In an embodiment, thedetector 46 can be a single detector that is used for detectingultraviolet intensity from all of the ultraviolet sources 44A, 44B. Forexample, the detector 46 can comprise an ultraviolet light emittingdiode operating in reverse bias. In this case, the detector 46 cancomprise a gallium nitride photodetector having a bandgap of the activelayer that is lower than the bandgap of the active layer of each of theultraviolet sources 44A, 44B.

In FIG. 10C, a trace gas detection component 110 can include multipleultraviolet sources, such as the ultraviolet sources 44A, 44B, that emitultraviolet radiation detected by an ultraviolet detector 46.Additionally, the trace gas detection component 110 can include afluorescent detector 112, which detects fluorescent radiation 114resulting from radiating the gas with ultraviolet light. The computersystem 20 can acquire and process data acquired by both detectors 46,112 to evaluate a density of the trace gas. It is understood that foradditional information, the computer system 20 can operate the differentultraviolet sources 44A, 44B asynchronously with different peakwavelengths in a pulsed time dependent mode of operation. Such operationcan enable the computer system 20 to obtain more information about themixture of gases that can be present in the media. In particular, thecomputer system 20 can implement a technique for measuring absorption ina mixture of gases, such as Differential Optical Absorption Spectroscopy(DOAS), in correlation with fluorescent spectroscopy to obtain precisedata on the concentration of one or more trace gases within the mixture.

A trace gas detection component described herein also can be used todetect a chemical gas that is not ultraviolet absorbing, but whichinteracts with an ultraviolet absorbing gas. To this extent, FIG. 11Ashows an illustrative chemical detection component 120 according to anembodiment. The chemical detection component 120 includes a first inlet122A through which a first gas can be introduced into a mixing chamber124 and a second inlet 122B through which a second gas can be introducedinto the mixing chamber 124. For illustration, the first gas can includea non-ultraviolet absorbing chemical that chemically reacts with anultraviolet absorbing chemical in the second gas. In an illustrativeembodiment, the first gas can comprise chlorofluorocarbon compounds,such as Freon, and the ultraviolet absorbing gas chemically interactingwith such compounds can comprise O₃. In an alternative embodiment, thefirst gas can comprise ClO₂, BrO₂, Cl and Br ions, and/or the like,interacting with O₃. It is understood that other embodiments ofcombinations of other gases are possible.

The gases can undergo a chemical reaction within the mixing chamber 124.The chemical reaction can be amplified by ultraviolet radiation having apeak wavelength selected to increase a rate of the chemical reaction.Additionally, the chamber 124 can include a mixing component 126 (e.g.,one or more fans), which can be operated by the computer system 20(FIG. 1) to improve the mixing of the gases within the mixing chamber124. In an illustrative application, the computer system 20 can firstdeliver the first and second gases into the chamber 124 and stop the gasdelivery after a predetermined amount of time. As the chemical reactiontakes place, the computer system 20 can acquire ultraviolet radiationdata using an ultraviolet emitting and detecting component 130, whichcan be configured as described herein. During progression of thechemical reaction, a concentration of gas that is ultraviolet absorbingdecreases due to the chemical reaction. This decrease can be measured bythe ultraviolet radiation component 130. The computer system 20 caninfer a rate of the chemical reaction from the rate of decrease of theultraviolet absorbing gas. FIG. 11B shows that absorption within thechamber is decreased at a rate correlated with the decrease ofconcentration of the second gas.

While shown and described herein as a method and system for detecting apresence and/or determining a concentration of a trace gas in anatmosphere (e.g., a sample gas), it is understood that aspects of theinvention further provide various alternative embodiments. For example,in one embodiment, the invention provides a computer program fixed in atleast one computer-readable medium, which when executed, enables acomputer system to detect the presence and/or determine theconcentration of the trace gas in the atmosphere. To this extent, thecomputer-readable medium includes program code, such as the detectionprogram 30 (FIG. 1), which enables a computer system to implement someor all of a process described herein. It is understood that the term“computer-readable medium” comprises one or more of any type of tangiblemedium of expression, now known or later developed, from which a copy ofthe program code can be perceived, reproduced, or otherwise communicatedby a computing device. For example, the computer-readable medium cancomprise: one or more portable storage articles of manufacture; one ormore memory/storage components of a computing device; paper; and/or thelike.

In another embodiment, the invention provides a method of providing acopy of program code, such as the detection program 30 (FIG. 1), whichenables a computer system to implement some or all of a processdescribed herein. In this case, a computer system can process a copy ofthe program code to generate and transmit, for reception at a second,distinct location, a set of data signals that has one or more of itscharacteristics set and/or changed in such a manner as to encode a copyof the program code in the set of data signals. Similarly, an embodimentof the invention provides a method of acquiring a copy of the programcode, which includes a computer system receiving the set of data signalsdescribed herein, and translating the set of data signals into a copy ofthe computer program fixed in at least one computer-readable medium. Ineither case, the set of data signals can be transmitted/received usingany type of communications link.

In still another embodiment, the invention provides a method ofgenerating a system for detecting a presence and/or determining aconcentration of a trace gas in an atmosphere. In this case, thegenerating can include configuring a computer system, such as thecomputer system 20 (FIG. 1), to implement the method of detecting apresence and/or determining the concentration of the trace gas in theatmosphere. The configuring can include obtaining (e.g., creating,maintaining, purchasing, modifying, using, making available, etc.) oneor more hardware components, with or without one or more softwaremodules, and setting up the components and/or modules to implement aprocess described herein. To this extent, the configuring can includedeploying one or more components to the computer system, which cancomprise one or more of: (1) installing program code on a computingdevice; (2) adding one or more computing and/or I/O devices to thecomputer system; (3) incorporating and/or modifying the computer systemto enable it to perform a process described herein; and/or the like.

The foregoing description of various aspects of the invention has beenpresented for purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formdisclosed, and obviously, many modifications and variations arepossible. Such modifications and variations that may be apparent to anindividual in the art are included within the scope of the invention asdefined by the accompanying claims.

What is claimed is:
 1. A system comprising: a chamber; a pumping systemfor introducing a sample gas into the chamber through an inlet: a filterfor filtering a trace gas from air prior to entering the chamber, a setof ultraviolet sources mounted on a first interior side of the chamber;an ultraviolet detector mounted on the first interior side of thechamber, wherein the chamber is defined by a plurality of reflectingwalls having an ultraviolet reflection coefficient of at least eightypercent; a set of beam guiding components optically coupled to the setof ultraviolet sources and the ultraviolet detector, wherein the set ofbeam guiding components is configured to lengthen the optical path ofthe ultraviolet beam between the set of ultraviolet sources and theultraviolet detector, and wherein the set of beam guiding componentsincludes a first reflective side and a second reflective side, whereinthe ultraviolet beam is reflected back and forth between the firstreflective side and the second reflective side before being directed tothe ultraviolet detector; a trace gas source configured to produce gashaving any of a plurality of known concentrations of the trace gas; anda computer system configured to: generate calibration data using thetrace gas source; evaluate the sample gas in the chamber for a presenceof a trace gas by: operating the pumping system with the filter removingthe trace gas from air entering the chamber; operating the pumpingsystem without the filter to introduce the sample gas into the chamberafter the trace gas has been removed; operating at least one of the setof ultraviolet sources; acquiring data corresponding to an intensity ofultraviolet radiation detected by the ultraviolet detector during theoperating at least one of the set of ultraviolet sources; anddetermining the presence of the trace gas using the acquired data andthe calibration data.
 2. The system of claim 1, further comprising: anoutlet, wherein the operating the pumping system with the filterremoving the trace gas includes: operating the pumping system with boththe inlet and the outlet open to allow at least three chamber volumes ofair to leave the chamber through the outlet; and sealing the chamberprior to operating the at least one of the set of ultraviolet sources.3. The system of claim 1, wherein the computer system operates the atleast one of the set of ultraviolet sources in a pulse mode having apulsing frequency.
 4. The system of claim 1, wherein the chamber isformed of: a first conical frustum having a first open base and a firstopen top; and a second conical frustum having a second open base and asecond closed top, wherein the first open top is attached to the firstinterior side of the chamber, and wherein the first open base isattached to the second open base, and wherein each of the first andsecond conical frustums has an opening angle in a range betweenapproximately twenty and approximately fifty degrees.
 5. The system ofclaim 1, wherein the set of ultraviolet sources include a plurality ofultraviolet sources, the plurality of ultraviolet sources including atleast two ultraviolet sources that emit ultraviolet radiation havingpeak wavelengths separated by at least ten nanometers.
 6. The system ofclaim 5, wherein the ultraviolet detector comprises a light emittingdiode operating in reverse bias.
 7. The system of claim 6, wherein theat least two ultraviolet sources comprise ultraviolet light emittingdiodes having bandgaps wider than a bandgap of the light emitting diodeof the ultraviolet detector.
 8. The system of claim 1, wherein thesystem includes means for adjusting a length of the optical path.
 9. Thesystem of claim 8, wherein the means for adjusting includes means formoving at least one beam guiding component of the set of beam guidingcomponents.
 10. The system of claim 1, wherein the ultraviolet beamtravels a first path through the set of beam guiding components in afirst direction and travels a second path through the set of beamguiding component in a second direction opposite the first direction,before being directed to the ultraviolet detector.
 11. The system ofclaim 1, wherein the trace gas is ozone.
 12. A system comprising: achamber having an inlet and an outlet; a pumping system for introducinga gas into the chamber through the inlet; a filter for filtering atarget gas from the gas prior to entering the chamber, an ultravioletsource located within an interior of the chamber; an ultravioletdetector located within an interior of the chamber; a set of beamguiding components optically coupled to the ultraviolet source and theultraviolet detector, wherein the set of beam guiding components isconfigured to lengthen an optical path of an ultraviolet beam betweenthe ultraviolet source and the ultraviolet detector, and wherein the setof beam guiding components includes a first reflective side and a secondreflective side, wherein the ultraviolet beam is reflected back andforth between the first reflective side and the second reflective sidebefore being directed to the ultraviolet detector; and a computer systemfor evaluating a sample gas in the chamber for a presence of the targetgas by: operating the pumping system with the filter removing the targetgas from pas entering the chamber; after operating the pumping systemwith the filter removing the target gas, operating the pumping system tointroduce the sample gas into the chamber, wherein the operatingincludes operating the pumping system with both the inlet and the outletopen for a sufficient time to allow at least three chamber volumes ofgas to leave the chamber through the outlet; sealing the chamber;operating the ultraviolet source in a pulse mode having a pulsingfrequency after the sealing; acquiring data corresponding to anintensity of ultraviolet radiation detected by the ultraviolet detectorduring the operating; and determining the presence of the target gas inthe sample gas using the acquired data, wherein the determining includesfiltering noise from the acquired data based on the pulsing frequency.13. The system of claim 12, wherein the operating the pumping systemwith the filter removing the target gas includes operating the pumpingsystem with both the inlet and the outlet open to allow at least threechamber volumes of air to leave the chamber through the outlet.
 14. Thesystem of claim 12, wherein the determining further uses calibrationdata corresponding to ultraviolet radiation intensities for a pluralityof known concentrations of the target gas, and wherein the computersystem evaluating the sample gas further includes determining whetherthe calibration data remains valid prior to the operating the pumpingsystem to introduce the sample gas.
 15. The system of claim 12, whereinthe computer system evaluating the sample gas further includes operatingthe pumping system to form a partial vacuum in the chamber prior to theoperating the pumping system to introduce the sample gas into thechamber.
 16. A method of evaluating a sample gas in a chamber for apresence of a target gas, the method comprising: a computer systemoperating a pumping system with a filter removing the target gas fromgas entering the chamber; the computer system operating the pumpingsystem without the filter removing the target gas to introduce thesample gas into the chamber, wherein the operating includes operatingthe pumping system with both an inlet and an outlet of the chamber openfor a sufficient time to allow at least three chamber volumes of gas toleave the chamber through the outlet; the computer system sealing thechamber; the computer system operating the ultraviolet source in a pulsemode having a pulsing frequency after the sealing; the computer systemacquiring data corresponding to an intensity of ultraviolet radiationdetected by the ultraviolet detector during the operating, wherein thechamber includes a set of beam guiding components optically coupled tothe ultraviolet source and the ultraviolet detector, wherein the set ofbeam guiding components is configured to lengthen an optical path of anultraviolet beam between the ultraviolet source and the ultravioletdetector, and wherein the set of beam guiding components includes afirst reflective side and a second reflective side, wherein theultraviolet beam is reflected back and forth between the firstreflective side and the second reflective side before being directed tothe ultraviolet detector; and the computer system determining thepresence of the target gas in the sample gas using the acquired data,wherein the determining includes filtering noise from the acquired databased on the pulsing frequency.
 17. The method of claim 16, wherein thedetermining further uses calibration data corresponding to ultravioletradiation intensities for a plurality of known concentrations of thetarget gas, and wherein the method further includes the computer systemdetermining whether the calibration data remains valid prior to theoperating the pumping system to introduce the sample gas.
 18. The methodof claim 17, wherein the method further includes generating newcalibration data in response to determining that the calibration data isno longer valid.
 19. The method of claim 16, wherein the method furtherincludes the computer system operating the pumping system to form apartial vacuum in the chamber prior to the operating the pumping systemto introduce the sample gas into the chamber.
 20. The system of claim12, wherein each of the ultraviolet source and the ultraviolet detectorcomprise light emitting diodes, wherein the computer system is furtherconfigured to selectively change operation of the light emitting diodessuch that: a first light emitting diode is operated as the ultravioletsource and a second light emitting diode is operated as the ultravioletdetector during a first sample gas evaluation; and the first lightemitting diode is operated as the ultraviolet detector and the secondlight emitting is operated as the ultraviolet source during a secondsample gas evaluation.